After importing references from various sources, you may have duplicate references in your Library. Zotero creates a sub folder for duplicates.
Zotero allows you to create Sub-Collections to organize references.
Simply drag and drop any references into Collections
Zotero provides free online storage space of 300MB allowing you to synchronize PDFs, images, web snapshots. Additional storage space need to be purchased.
If you do not want associated pdfs and snapshots to be attached while adding references in order to save the storage space, in Zotero, click Edit <Preferences < General. In File Handling untick 'Automatically take snapshots when creating items from webpages' and 'Automatically attach associated PDFs and other files when saving items'. (These options are selected by default)
